A. Windows 7 introduced location-aware printing, which lets a different default printer be specified based on the network a computer is connected to, as shown here.
To use location-aware printing, open the Devices and Printers Control Panel applet, select a printer, then click Manage default printers. Now you can set the option to Change my default printer when I change networks. Select the networks known to the machine and the printer that should be used as the default for the location.